1. Field of the Invention
The present invention relates generally to structures having movable members which operate under ice-forming conditions, and more particularly to a contact assembly for a high-voltage switch.
2. Description of Related Art
Various arrangements are provided for high-voltage switches to prevent ice from forming on critical portions of contact structures; e.g., to avoid the accumulation of ice that might inhibit or prevent suitable cooperation of contacts.
A first type of ice-excluding design utilizes plate-like shields or hoods which are generally rigid and enclose or shield the contact assembly. The shield is arranged so as not to interfere with the operation of a movable contact with a contact assembly.
Another type of ice-excluding arrangement provides flexible shields which move out of the way when acted upon by the movable contact. For example, U.S. Pat. No. 4,296,284 discloses such an arrangement.
While these arrangements may be generally suitable for their intended purposes, neither of these two basic approaches prevents the ingress of moisture to critical portions of the contact structure. Additionally, the fixed shields are rather cumbersome and expensive and, under some environmental conditions, are not even totally effective in preventing precipitation from directly entering the contact structures. The flexible shields are also not totally effective under all circumstances and, additionally, complicate the operation of the switch; either by requiring appropriate mechanisms for moving the flexible shield out of the way during operation or by requiring that the moving contact engage the flexible shield. Further, the shields themselves are also subject to being bound up by ice or corrosion.